1. Field of the Invention
The present invention relates to a mechanical pencil, and in particular, to a knocking-type mechanical pencil in which a remaining or unconsumed lead portion is pressed out by a following or next lead portion, and in which the remaining lead portion can be used until its length is shortened.
2. Background Art
FIG. 9A shows a conventional knocking-type mechanical pencil in which a remaining lead portion can be used until its length is shortened. The conventional knocking-type mechanical pencil has a cylindrical main body 1 and a lead-feeding mechanism disposed in the main body 1. The lead-feeding mechanism comprises a lead tank 3 containing a lead 2, a collet chuck 4 connected to the lead tank 3, a clutch 5 for clutching the collet chuck 4, and a spring 6 for biasing the lead tank 3 rearwardly. A mouthpiece 7 is connected to the main body 1, and a slider 13 extends into the mouthpiece 7. A lead-holding member 9 is disposed in the slider 13 and extends near to a front end of the slider 13 so as to hold the remaining lead portion. When a rear end portion of the lead tank 3 is knocked, since the collet chuck 4 is clutched by the clutch 5 at a lead-gripping position, the collet chuck 4 advances while gripping the lead 2. Then, when a flange of the clutch 5 abuts on a stepped portion 8 disposed in the mouthpiece 7, the collet chuck 4 comes out of the clutch 5 and its front end widens, whereby the lead 2 is released from gripping. At this time, the lead 2 is inserted into the lead-holding member 9 disposed in the mouthpiece 7 and is held at the advanced position by friction of the lead-holding member 9. When the knocking is stopped, the collet chuck 4 is moved backwardly by the action of the spring 6, and during this backward movement, the clutch 5 clutches the collet chuck 4 and the lead 2 is thereby gripped gradually. When the flange of the clutch 5 abuts on a shoulder portion 10, the collet chuck 4 returns to the gripping position and the lead 2 can be firmly gripped. As mentioned above, since the chuck 4 grips the lead 2 on its return to the gripping position from the advanced position and the lead 2 is transferred, the lead 2 moves backwardly a little from the advanced position.
The lead-holding member 9 has a lead insertion hole 11 and is made of an elastic material, such as rubber, so that it frictionally holds the lead 2. The lead-holding member 9 extends to near a front end in a slider 13 which is slidably fitted in a bore 12 of the mouthpiece 7. Inside the mouthpiece, a slider-resisting member 14 is disposed in contact with the periphery of the slider 13 so that a frictional resistance larger than a frictional resistance of the lead-holding member 9 is applied to the slider 13. By this structure, when the collet chuck 4 is moved to the advanced position by the knocking operation, the slider 13 is pushed forward and advances together with the chuck 4. When the front end of the slider 13 abuts on the paper surface and is pressed backwardly, the slider 13 moves backwardly, but when the mechanical pencil is not used, the slider 13 will not unnecessarily protrude or retract.
During a writing operation, the lead 2 of the mechanical pencil is fed out to such an extent that the front end of the lead 2 protrudes slightly outwardly from the front end of the slider 13. However, when the lead 2 is shortened or consumed and is no longer gripped by the collet chuck 4, a space 15 is formed between a remaining lead portion 2a and a following lead portion 2b as shown in FIG. 9A. Namely, as mentioned above, when the lead 2 returns from the advanced position to the gripping position by the lead-feeding mechanism, at the moment when the collet chuck 4 is engaged with the clutch 5, the collet chuck 4 returns clamping the following lead portion 2b, but the remaining lead portion 2a remains at the advanced position, whereby the space 15 will be formed between the remaining and following lead portions 2a, 2b. Accordingly, if the writing operation is continued, the remaining lead portion 2a slips within the lead-holding member 9 and moves backwardly until it abuts on the following lead portion 2b since the movement of the lead-holding member 9 is frictionally restrained by the slider-resisting member 14. As a result, the protruded front end of the lead 2 retracts in the distance of the space 15 (FIG. 9B). Accordingly, there have been drawbacks that the writing operation can not be continued and further knocking of the mechanical pencil is necessary.